Downregulation of miR156-Targeted PvSPL6 in Switchgrass Delays Flowering and Increases Biomass Yield

Jinjun Cai; Wenwen Liu; Weiqian Li; Lijuan Zhao; Gang Chen; Yangyang Bai; Dongmei Ma; Chunxiang Fu; Yamei Wang; Xinchang Zhang

doi:10.3389/fpls.2022.834431

Downregulation of miR156-Targeted PvSPL6 in Switchgrass Delays Flowering and Increases Biomass Yield

Front Plant Sci. 2022 Feb 18:13:834431. doi: 10.3389/fpls.2022.834431. eCollection 2022.

Authors

Jinjun Cai^{1

2}, Wenwen Liu³, Weiqian Li², Lijuan Zhao^{3

4}, Gang Chen², Yangyang Bai², Dongmei Ma⁴, Chunxiang Fu^{3

5}, Yamei Wang³, Xinchang Zhang¹

Affiliations

¹ College of Natural Resources and Environment, Northwest Agriculture and Forestry University, Yangling, China.
² Institute of Agricultural Resources and Environment, Ningxia Academy of Agriculture and Forestry Sciences, Yinchuan, China.
³ Shandong Provincial Key Laboratory of Energy Genetics and CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, Qingdao, China.
⁴ Breeding Base for State Key Laboratory of Land Degradation and Ecological Restoration in Northwest China, Ningxia University, Yinchuan, China.
⁵ CAS Key Laboratory of Tibetan Medicine Research, Northwest Institute of Plateau Biology, Xining, China.

Abstract

MiR156/SQUAMOSA PROMOTER BINDING-LIKEs (SPLs) module is the key regulatory hub of juvenile-to-adult phase transition as a critical flowering regulator. In this study, a miR156-targeted PvSPL6 was identified and characterized in switchgrass (Panicum virgatum L.), a dual-purpose fodder and biofuel crop. Overexpression of PvSPL6 in switchgrass promoted flowering and reduced internode length, internode number, and plant height, whereas downregulation of PvSPL6 delayed flowering and increased internode length, internode number, and plant height. Protein subcellular localization analysis revealed that PvSPL6 localizes to both the plasma membrane and nucleus. We produced transgenic switchgrass plants that overexpressed a PvSPL6-GFP fusion gene, and callus were induced from inflorescences of selected PvSPL6-GFP_OE transgenic lines. We found that the PvSPL6-GFP fusion protein accumulated mainly in the nucleus in callus and was present in both the plasma membrane and nucleus in regenerating callus. However, during subsequent development, the signal of the PvSPL6-GFP fusion protein was detected only in the nucleus in the roots and leaves of plantlets. In addition, PvSPL6 protein was rapidly transported from the nucleus to the plasma membrane after exogenous GA₃ application, and returned from the plasma membrane to nucleus after treated with the GA₃ inhibitor (paclobutrazol). Taken together, our results demonstrate that PvSPL6 is not only an important target that can be used to develop improved cultivars of forage and biofuel crops that show delayed flowering and high biomass yields, but also has the potential to regulate plant regeneration in response to GA₃.

Keywords: PvSPL6; biomass yield; flowering; gibberellin; subcellular localization; switchgrass.